The present invention relates to a pressure booster system for fluids. The system of the present invention defines particular application in the liquid chromatography field where it is necessary to deliver fluids at high pressure with a minimum of pulsation and at an accurate flow rate.
A typical liquid chromatography system employs a packed column to effect the separation of solute from a liquid sample. A detector analyzes the outflow from the column to identify particular components in the solute. Many chemical components exhibit similar elution characteristics and therefore exit the packed column at nearly the same time. Therefore, forcing the liquid sample through the column smoothly in a continuous and well defined flow rate is essential to the obtaining of accurate analyses. Prior liquid chromatography systems employ high pressure pumps, of the positive displacement type, to force the liquid sample through the packed column. Unfortunately, piston or piston-like pumps inherently produce an output flow having pulsations. High pressure piston pumps depend on proper operation of check valves for precise flow rate delivery. Although the use of dual piston pumps with overlapping cam characteristics have eliminated a portion of the flow pulsation, elaborate feedback controls are necessary to further reduce pulsations.
In this regard reference is made to U.S. Pat. No. 3,917,531 to Magnussen which describes a flow feedback system which employs a flow transducer to vary the motor speed of the pump according to a feedback signal. A solvent system described in U.S. Pat. No. 3,398,689 to Allington discloses a proportioning system for liquid chromatographic applications which utilize motor velocity feedback as a method of varying the pumping rate of the liquid. U.S. Pat. No. 3,932,078 to Ball et al employs a control means which measures the pressure during the pumping period of one piston and transforms the same into a pressure standard for a second piston, which operates under an overlapping cam arrangement.
All of the prior art systems require precision built high pressure metering pumps and feedback controls which must adjust for a multitude of corrections as an adjunct to liquid characteristics operating at high pressures. Prior art precision solvent metering pumps are expensive to construct and are markedly less reliable than other components of a liquid chromatographic system.